Attachment plug



July 26, 1927. 1,636,798

E. c. BALLMAN ATTACHMENT PLUG Filed Nov. 1923 Patented July 26, 1927.

EDWIN C. BALL'MAN, OF ST. LOUIS, MISSOURI.

ATTACHMENT PLUG.

Application filed November 9, 1923. Serial No. 673,690.

This invention relates to electrical attachment plugs and the like.

Attachment plugs of this kind are ordinarily constructed of fragile material, such a as porcelain, molded insulation and the like,

which are subject to breakage in case the plug should be dropped on a hard surface.

The construction of the plug is usually such.

that the part constructed of fragile material has the form of a more or less enlarged head. This head or enlarged body forms the most prominent part of the plug structure and the one most liable to receivethe shock of the fall. Furthermore such a plug often is attached to the end of a flexible cord so that there are frequent occasions when the plug 'is swung at the end of the cord and is thus liable to strike against objects with the result that the fragile part is broken.

One of theobjects of this invention, therefore, is to provide an attachment plug which shall be guarded against accidental breakage by dropping or striking against hard objects.

Another object of this invention is to provide such a plug which shall be cheap to manufacture and durable in service.

Further objects will appear from the detail description taken in connection with the accompanying drawing, in which: 1

Figure l is a side View of an attachment plug embodying this invention;

and

Figure 2 represents a series of cross-sec tional views showing buffers of different shapes.

Referring to the accompanying drawing 1 designates the contact shell of an ordinary screw plug having a central contact 2 and an insulating body 3 which may be surmounted by an enlarged head 4;. The enlarged head 4 and the body 3 may in some instances be merged into the same part. In other instances the head 4 may form part of a separable plug having blades engaging sockets in the part 3. In most instances, however, the parts 3 or 4 are somewhat enlarged in comparison with the screw shell 1 so that if the plug should be dropped, the

former would be the most liable to strike 4 Since the body or head 4 is usually constructed of more or less fragile insulating material, such as porcelain or the various forms of molded insulation, these plugs are subject to a considerable amount of breakage due to rough handling. In accordance with this invention the body or head l may be grooved along its circumference to receive a shock absorbing buffer 5 in the form of a ring of soft rubber or other resilient or yielding material adapted to absorb any shocks and thereby protect the fragile material against breakage. The bufler 5 is preferably placed at or about the most enlarged and most prominent part of the head so that it will effectively protect the other portions. Reference to Figure 1 will show that the plug in falling can strike the ground only at the points touched by the dotted lines. One of these touches the shell which being of metal is well able to withstand shocks. Another point of contact is at the buffer 5 and a third at the leads 6 where they emerge from the head 4. It will be evident, therefore, that in falling this plug can strike only on the buffer 5 and at such other portions as are capable of withstanding the fall without danger.

The simplest form of buffer is, of course, a plain rubber ring of circular cross-section held in the groove by its own elasticity. Figure 2, however, shows rings of other cross-sections which may be adapted to particular purposes. If necessary a retaining element in the form of a wire 7 may be added to secure the ring in place.

It is obvious that various changes may be made in details of construction without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is:

1. An electrical attachment plug, of fragile materials, having an annular recess therearound at the point of greatest diameter, a contact shell projecting from one side side of said head, a resilient ring mounted 0 thereof, a lead from the other side thereof, in said recess and encircling said head in and a resilient ring mounted in said recess order to protect the same against breakage, and encircling said plug in order to protect said ring being encircled by a reinforcing the same against breakage. binder.

2. An electrical attachment plug compris- In testimony whereof I afiix my signature 15 ing a fragile head having an annular recess this 29th day of Oct, 1923. therearound, a contact shell projecting from one side of said head, a lead from the other EDWIN C. BALLMAN. 

